In the mid-1800s, French president Louis Napoléon transformed his capital city in a project of unprecedented scale and extravagance, writes Lewis Jones.

After the revolution of 1848, Louis-Philippe, France's Citizen King, went into exile in Surrey, taking with him his much-mocked umbrella, and was succeeded by Louis Napoléon, nephew of Bonaparte. Karl Marx thought him "a grotesque mediocrity", and Victor Hugo, who called him "Napoléon le Petit", was so disgusted by him that he left France for 20 years.

But the French elected Louis Napoleon president, and after his coup d'état in 1851, confirmed him by referendum first as Prince-Président, and then as Emperor. His enduring achievement, as Rupert Christiansen demonstrates in his elegant and gorgeously illustrated new book, was to transform Paris from the city of Hugo's Les Miserables to that of Proust's À la recherche du temps perdu.

During his exile in London, Louis Napoléon had admired architect John Nash's grand remodelling of the city, and was resolved to do the same for Paris. In 1852, he found the man to realise his dream in Georges-Eugène Haussmann, a clever but unimaginative manager, to whom he gave carte blanche. On his first day at work, the Emperor showed him a map he had sketched in crayon, since lost, showing a network of boulevards that would cut through the old city and allow it to breathe, which would be his blueprint.

It was a project of unprecedented scale and extravagance. The ancient Tour St Jacques, for example, was suspended on timber scaffolding while the hillock it stood on was removed. Paris already had rows of five- or six-storeyed apartment blocks, but Haussmann put them everywhere, in limestone, with roofs of zinc or slate. Private, comfortable and clean, they made ideal homes for the rising bourgeoisie.

Amid all this regimentation stood the dazzling new opera house designed by Charles Garnier, which Christiansen describes with zest. He allows that "there is something disconcertingly promiscuous about the design", but it "represents the zenith of the Second Empire's cultural pretensions and remains to this day a building encrusted with all the grandeur of French amour propre".

Haussmann, he writes, "had an almost pathological hatred of blockage - one can detect in him symptoms of an obsessive-compulsive disorder" - and was vindictive in his treatment of the Île de la Cité, a district "crisscrossed by damp, twisted and filthy streets" and "choked by a mass of shacks", which he hated, having been obliged as an asthmatic schoolboy to cross it on his way to and from his lycée.

Victor Fournel called him "the Attila of the straight line", and complained that he had made "a city of shops and cafés... destined to become one great big hotel for foreign tourists". This new Babylon boasted more than 20,000 cafés, many of them serving absinthe, and in "suburban dives" the can-can was performed, "in which the women wore nothing underneath their skirts and their high kicks were an invitation to an orgy".

There were 50,000 cases of venereal disease a year, and some 30,000 prostitutes. "They are everywhere," said the prefect of police, "even in train carriages. They circulate in great numbers on the most beautiful boulevards, to the great disgust of the public."

Haussman built five town halls for the new arrondissements created by his scheme, four bridges across the Seine, and the airy new Les Halles. And he transformed the Bois de Boulogne from a wasteland into something to rival Hyde Park, made the Bois de Vincennes in the east, the pretty Parc Monceau in the 8th, and the Buttes-Chaumont from an old quarry that had been a dumping ground for dead horses.

He also built what was the world's biggest reservoir, and magnificent new sewers. But his concern for hygiene would be his undoing. Planning a vast new necropolis, he used a front company to acquire land in a manner that was not quite straightforward, and in January 1870, the Emperor dismissed him.

In September, after Bismarck had tricked him into a disastrous war, Louis Napoléon was himself dismissed - deposed, at any rate - and went into exile in Kent with his "ghastly wife Eugenie". But "Haussmannisation" proved unstoppable. Three times as many new buildings were erected between 1878 and 1888 as had been between 1860 and 1869, and the Second Empire style was imitated in the Avenue Louise in Brussels, the Grand Boulevard in Budapest and around London's Victoria station.

The replacement of cramped squalor with spacious theatrical spectacle was deplored as ruthless vulgarity by Gustave Flaubert and Charles Baudelaire, who mourned the loss of the old Paris's unexpected charms, and even Garnier, who acknowledged the beauty of the "big straight streets", found them "as cold and stiff as a dowager". But it must be admitted that they have worn well.